Officially Nav lights should be turned ON when the aircraft is occupied by the crew, Beacon lights should be turned ON prior to engine start, and remain ON until after engine shutdown, Strobe and Landing lights should be turned on just prior to takeoff, Strobes remain ON during flight and are turned OFF once you have exited the runway after landing, Landing lights are OFF above 10000ft and ON again when descending below 10000ft. Hope this helps.